A security device may be utilized to provide security measures to an electronic device that may incorporate the security device or be coupled to it. The security measures may comprise authentication (e.g., authentication of devices, users, or activities), and/or encryption measures (e.g., encrypting or decrypting exchanged data). A transaction or access via the security device may be authenticated by communicating an authentication request by the security device to an authentication server, which may generate, in response, a sequence of information requests that are sent to the security device. The security device may then generate, in response, a sequence of responses that are sent to the authentication server, with the sequence of responses comprising a sequence of reported values each of which are unique. The authentication server may then authenticate the security device based on comparing of the sequence of reported values with a sequence of expected values that identifies the security device.